Hydrocarbon conversion process for production of benzene and substantially olefin-free gasoline blending stock



CAT. GASOLINE Nov. 26, 1968 A. H.. PETERSON ET AL 3,413,210

HYDROCARBON CONVERSION PROCESS FOR PRODUCTION OF BENZENE AND SUBSTANTIALLY OLEFIN-FREE GASOLINE BLENDING STOCK Filed May 29, 1967 i-C5 TO GASOLINE BLENDING C5 TO GASOLINE BLENDING I I I l I A l I I I I C7+GASOLINE I I l I ISOMERATE I I TO GASOLINE -/R BLENDING I L I I 1 I I I \0 GASOLINE AROMATICS TO SEPARATION NORMAL FEED RAFFINATE TO BTX REFORMER INVEN TORS JOE I KELLY ALAN H. PVRSON United States Patent 3,413,210 HYDROCARBON CONVERSION PROCESS FOR PRODUCTION OF BENZENE AND SUBSTAN- TIALLY OLEFIN-FREE GASOLINE BLEND- ING STOCK Alan H. Peterson and Joe T. Kelly, Littleton, Colo., assignors to Marathon Oil Company, Findlay, Ohio, a corporation of Ohio Filed May 29, 1967, Ser. No. 646,441 9 Claims. (Cl. 208-79) ABSTRACT OF THE DISCLOSURE The present invention comprises a hydrocarbon conversion process for the production of both benzene and -a substantially olefin free gasoline blending stock from a gasoline produced by cracking of hydrocarbons, and a raflinate from the extraction of a hydrocarbon stream from a catalytic reformer, the steps comprising in combination:

(a) Fractionating said gasoline and said raflinate either singly or commingled to remove hydrocarbons of about 0; and higher;

(b) Hydrogenating at least a portion of the effluent from said fractionation step under conditions sufficient to hydrogenate substantially all of the olefins present in the effluent from said fractionation step;

(c) Isomerizing at least a portion of the effluent from said hydrogenation step in the presence of a catalyst to produce an isomerized stream having substantially more branching than does the feed to said isomerization step;

(d) Fractionating at least a portion of said isomerized stream to separate out an isomerate suitable for gasoline blending;

(e) Catalytically reforming a hydrocarbon stream to produce a reformate containing both aromatics and non-aromatics;

(f) Separating a major portion of said aromatics from at least a portion of said reformate stream thus producing a predominantly paraffinic stream;

(lg) Combining at least a portion of said primarily paraffinic stream with said catalytic gasoline or the hydrogenated product therefrom prior to the isomerization step.

Benzene is useful for solvent application and as a starting material for various petrochemicals and other organic compounds. Gasoline blending stocks free of highly volatile olefins are preferred as fuels for motor vehicles because olefins tend to enter into certain photochemical reactions which may tend to cause atmospheric pollution.

BACKGROUND OF THE INVENTION Field of the invention-The present invention relates to the manufacture of gasoline blending stocks from oatalytically produced gasoline, and in particular relates to processes for the simultaneous manufacture of such blending stocks and of benzene.

Description of the prior art.--'Ihe individual hydrocarbon conversion processes which comprise the present invention are well known. The catalytic production of gasoline by molecular cracking of gas oils and other suitable feed stocks, hydrogenation processes for the complete or partial hydrogenation of unsaturates, isomerization processes for producing various isomerized products, catalytic reforming processes for the production of aromatics, and processes for the separation of such aromatics have all been known individually. However, to the best of our knowledge, the literature has Patented Nov. 26, 1968 ice never previously described a process for the simultaneous production of gasoline blending stocks which are substantially free from undesirable olefins and simultaneous production of valuable benzene by the combination of the above mentioned conventional individual steps.

SUMMARY According to the present invention, catalytically or thermally cracked gasolines are hydrogenated to substantially saturate the olefins contained in the gasoline, then preferably fractionated to remove isopentane and all lower hydrocarbons. These removed materials may generally be used for gasoline blending. The remaining stream is then isomerized conventionally to increase the average number of branches per molecule. The isomerate is preferably removed by fractional distillation and utilized preferably for gasoline blending. The remaining stream, after removal of the isomerate, can then be fed to a reforming step.

As an alternate to the above fractionation to remove the isomerate, the entire feed stream from the isomerization step may be utilized as substantially olefin free gasoline blending stock.

The catalytic reforming step involves the feeding of a suitable hydrocarbon feed to a catalytic reformer of conventional design and operation to produce an aromatic-non-aromatic reformate which is preferably fractionated to remove C and lower hydrocarbons for gasoline blending. The remaining reformate stream can then be separated into a paraflinic and an aromatic portion by conventional methods, eg by solvent extraction techniques such as the well known Udex process described in 45 Hydrocarbon Processing, No. 9, 236, September 1966.

The aromatics from the separation consist primarily of benzenes and alkyl benzenes. In preferred embodiments in which the bottoms, after separation of isomerate, constitute the entire feed to the reformer, the aromatics separated fiom the aromatic-non-aromatic reformate stream Will constitute principally benzene. In other embodiments Where the normal feed to a reformer used for the production of benzene, toluene and/or xylenes is added to these bottoms remaining after the separation of the isomerate and the resulting mixture is fed to the catalytic reformer, the above mentioned mixture of benzenes and alkyl benzenes will be produced in the aromatic extraction step.

The remaining paraffinic fraction of the products produced by the aromatic extraction step is fed back to join the main stream prior to the isomerization step. That is, this parafiinic fraction is either mixed directly with the catalytic gasoline prior to fractionation to remove C and higher hydrocarbons or, suitably fractionated, prior to the hydrogenation step or, fed directly to the isomerization step after similar suitable fractionation.

The gasoline basic feed stream from the process may be either catalytically cracked by one of the conventional catalytic cracking processes, e.g. fluid catalytic cracking- Universal Oil Products as described in 43 Hydrocarbon Processing No. 9, p. 150, September 1964, or the gasoline may be derived from thermal cracking, e.g. as overhead from a coking step. Typically such gasolines contain from roughly 5 to as much as 50%, or even more olefins. All percents herein being by weight.

In general, the hydrogenation step will be accomplished by any suitable catalytic hydrogenation method with the hydrogen consumption being adjusted to substantially saturate the feed material. In most cases lighter hydrogenation processes such as the hydrotreating types of processes described at 43 Hydrocarbon Processing No. 9, pages 188-196, September 1964, can be utilized. Where benzene is present in the gasoline feed to the hydrogenation unit more rigorous hydrogenation processes may be utilized. In some cases it may even be preferable to use a two step hydrogenation process to minimize gum formation and/ or to obtain complete hydrogenation of benzene.

The effluent from the hydrogenation step is preferably separated in a deisopentanizer which conventionally removes isopentane and lower materials for gasoline blending or other purposes.

The isomerization step is also conventional and any of the well known processes such as Universal Oil Products Penex Process, Standard Oil of Indianas Light Naphthaisornerization, or other processes such as those described at 43 Hydrocarbon Processing No. 9, pp. 175-180, September 1964 may be utilized. Low temperature processes which produce high octane products without recycle and which minimize cracking of naphthenes are particularly desirable.

The product from the isomerization step is itself suitable for gasoline blending in its entirety. However, it is preferred that the effiuent from the isomerization step be split to produce as overhead an isomerate boiling above about 160 F. with the bottoms being a predominately naphthenic fraction, particularly desirable as feed stock for the reforming step.

This naphthenic fraction can be fed to the catalytic reformer. Alternatively the catalytic reformer may be fed from some other source of suitable hydrocarbons. A third possibility which will be particularly desirable in refineries having only a single BTX reformer, will be the use of a combined feed consisting of the naphthenic bottoms remaining after fractionation of the isomerate, together with a normal reformer feed produced from some other source of hydrocarbons in the refinery.

The reforming step can utilize any of the conventional reforming processes such as Universal Oil Products Platforming Process, Standard Oil of Indianas Ultraforming, or the other reforming processes described at 43 Hydrocarbon Processing No. 9, pp. 158-164, September 1964.

The reformate is preferably fractionated to remove C and lower materials for gasoline blending or other purposes.

The bottoms from this fractionation step are then run to the aromatic separation step. Liquid-liquid extraction processes such as the Udex Process of Universal Oil Products may be utilized. In specialized circumstances, selective absorption, or other processes from the separation of 4 aromatics may be desirable in place of the solvent extraction technique.

As stated before, the aromatics from the aromatic separation step will consist primarily of benzene where the feed to the reformate consisted primarily of the bottoms after separation of the isomerate. Where other suitable hydrocarbon feed streams are utilized as reformer feed in place of, or in conjunction with, said bottoms after separation of isomerate, the feed stream will also contain alkyl benzenes in quantities varying with the composition of the reformate feed.

DESCRIPTION OF THE DRAWING The drawing is a schematic diagram of a preferred embodiment of the present invention.

PREFERRED EMBODIMENT OF THE INVENTION As shown in the drawing, a 400 F. end point gasoline stream A from a fluid catalytic cracking unit is fractionated in an efiicient distillation column 1 of conventional design with materials boiling below about 162 F. taken overhead as feed to the hydrogenation reactor 2. The hydrogenation is carried out at about 500 F. and 1000 p.s.i.g. over a sulfided nickel (6%) tungsten (19%) on alumina catalyst at a liquid hourly space velocity of 2.0 and hydrogen feed rate of 4000 s.c.f. per bbl. After stripping of hydrogen and other light gases the product from the hydrogenation reactor 2 has the approximate composition D shown in the table. This hydrogenated stream D is combined with recycle stream R to give composition E and fractioned in column 3 to remove isopentane and materials boiling below about 87 F. as an overhead gasoline blending stock F. The bottoms fraction from column 3 having the approximate composition G is isomerized at 350 F. and 1000 p.s.i.g. with a liquid hourly space velocity of 1.0 and hydrogen flow of about 3000 s.c.f./bbl. using a heavily chlorided platinum or alumina catalyst prepared as described in US. Patent 3,248,320 (British Petroleum Co. Ltd. Apr. 26, 1966). The isomerization product has the approximate composition and volume H shown in the table. The isomerization product H is fractioned to a cut point of about 159 F. in column 5 to yield as overhead a gasoline blending stock I having a Research Octane rating of Approximate Stream Compositions (bbl./day) A B C D E F G H I J C and lighter 20 20 i-C 1,060 10 620 nC 790 750 175 Cyclopentane 50 100 90 2,2-dirnethylbutane. 10 160 760 2,3-dimethylbutan" 190 250 2-methylpcntane 350 950 870 3 -metl1ylpentane 240 670 490 n-Hexane 200 740 350 Methylcyclopentane. 150 420 200 Cyclohexane 30 200 Heavier than cyclohexane 20 40 40 Olefins 2, 240 900 1, 340 Nil Nil Nil Nil Nil Nil Nil Total stream 8,000 3, 000 5,000 3,000 5, 230 1, 4, 4, 120 3, 690 430 Approximate Stream Compositions (bbl./day) K L M N O P Q R S C4 and lighter 5 5 300 300 i- 5 20 2O Il-C5 c c 80 Cyclopentane 30 30 9 2-dimethylbutanc. 10 10 2,3dimethylbutane 25 25 Z-methylpentane 210 210 3-methylpentane 170 n-Hexane 890 890 Methyleyclopentane 580 770 Cyclohexane 570 770 Heavier than cyclohexane 1." 6,630 6,670 Olefins Nil Nil Total stream 9, 220 9,650 8, 660

Benzene.

approximately 83.8 clear and 101.7 at 3 cc. of tetraethyl lead per gallon when combined with gasoline blending stock F. The bottom cut from distillation column 5 has the approximate composition I and is combined with a normal B-T-X Reformer feedstock K and reformed in a Universal Oil Products Platformer 6 under normal conditions for benzene-toluene formation. The eflluent from the reformer 6 is stripped of hydrogen and accompanying gases to give composition M which is fractioned in column 7 to remove material boiling below about 100 F. to give a gasoline blending stock N and a bottoms cut 0 which is extracted in a Universal Oil Products Udex solvent extraction system (Hydrocarbon Processing 45, #9, 236 September 1966) to give an aromatic concentrate P and ratfinate Q. Raflinate Q can be directly commingled with gasoline feed stream A or more preferably can be fractioned in column 9 to a cut point of about 162 F. to give an overhead product R for recycle to column 3 and a bottoms product S suitable as a gasoline blending stock, as shown by dashed lines in the drawing.

In normal operation of the reformer and Udex unit without inclusion of J in the feed the benzene yield is reduced by about 290 bbl./d. to a quantity of about 630 hbL/d.

What is claimed is:

1. In a hydrocarbon conversion process for the production of both benzene and a substantially olefin free gasoline blending stock from a gasoline produced by cracking of hydrocarbons and a rafiinate from the extraction of a hydrocarbon stream from a catalytic reformer, the steps comprising in combination:

(a) Fractionating said gasoline-raffinate feed either singly or comingled to remove hydrocarbons of about C and higher;

(b) Hydrogenating at least a portion of the effluent from said fractionation step under conditions sufiicient to hydrogenate substantially all of the olefins present in the effiuent from said fractionation step;

(c) Isomerizing at least a portion of the efiluent from said hydrogenation step in the presence of the catalyst to produce an isomerized stream having substantially more branching than does the feed to said isomerization step;

(d) Fractionating at least a portion of said isomerized to separate out as a more volatile fraction an isomerate suitable for gasoline blending and a less volatile fraction;

(e) Catalytically reforming a hydrocarbon stream comprising at least a portion of said less volatile fraction from said isomerate fractionation step to produce a reformate containing both aromatics and non-aromatics;

(f) Separating a major portion of said aromatics from :at least a portion of said reformate stream, thus producing a predominantly parafiinic stream;

g) Combining at least a portion of said primarily paraffinic stream with said catalytic gasoline or the hydrogenated product prior to the isomerization step.

2. The process of claim 1 wherein the feed to said aromatic separation step is fractionated to remove C and lower hydrocarbons.

3. The process of claim 1 in which said aromatics are separated by a solvent extraction process.

4. The process of claim 1 wherein at least a portion of said paraflinic stream is combined with said catalytic gasoline prior to said hydrogenation step.

5. The process of claim 1 wherein the feed to said aromatic separation step is fractionated to remove C and lower hydrocarbons.

6. The process of claim 1 in which said aromatics are separated by a solvent extraction process.

7. The process of claim 1 wherein at least a portion of said paraffinic stream is combined with said catalytic gasoline prior to said hydrogenation step.

8. The process of claim 5 in which said aromatics are separated by a solvent extraction process.

9. The process of claim 5 wherein at least a portion of said paraflinic stream is combined with said catalytic gasoline prior to said hydrogenation step.

References Cited UNITED STATES PATENTS 7/1962 Swartz 208-79 11/ 1967 Drehman 208-63 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,413,210 November 26, 1968 Alan Peterson et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, line 44, after "isomerized" insert stream Signed and sealed this 10th day of March 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Attesting Officer Commissioner of Patents WILLIAM E. SCHUYLER, JR. 

